Dài thế ai trả lời đc?!chia thành từng câu chứ

Phần b

399 x 45+55 x 399 = 399 x ( 45 + 55 ) = 399x100 =39900 / 1995x(1996-1991)= 399x20x5/399x5x5=20/5=4

bạn chưa học khái niệm phân số à

5/17x21/4x47/15x0= 5/17x21/4x47/0 nên mẫu là 0 thì số đó không  là phân số

a) \(\frac{399\times45+55\times399}{1995\times1996-1991\times1995}=\frac{399\times\left(45+55\right)}{1995\times\left(1996-1991\right)}=\frac{399\times100}{399\times5\times5}=4\)

b) \(\frac{1996\times1995-996}{1000+1996\times1994}=\frac{1996\times\left(1994+1\right)-996}{1000+1996\times1994}=\frac{1996\times1994+1996-996}{1000+1996\times1994}\)

\(=\frac{1996\times1994+1000}{1000+1996\times1994}=1\)

c) \(\frac{637\times527-189}{526\times637+448}\)bạn làm tương tự ý b).

d) \(\frac{677\times874+251}{678\times874-623}\)bạn làm tương tự ý b). 

=0 nha bạn

1996 x 1995 - 996 - 1000 - 1996 x 1994

= 1996 x 1995 - 1996 - 1996 x 1994

= 1996 ( 1995 - 1 - 1994 )

= 1996 . 0

= 0

1996x1995-996-1000-1996x1994=0

`(399 xx 45 + 55 xx 399)/(1995xx1996-1991xx1995)`

`= (399xx(45+55))/(1995xx(1996-1991))`.

`= (399xx100)/(1995xx5)`

`= (399 xx 5 xx 5 xx 4)/(1995 xx 5)`

`= 4`.

\(\dfrac{399\times45+55\times399}{1995\times1996-1991\times1995}\)

\(=\dfrac{399\times\left(45+55\right)}{1995\times\left(1996-1991\right)}\)

\(=\dfrac{399\times100}{1995\times5}\)

\(=\dfrac{399\times5\times5\times4}{399\times5\times5}\)

\(=\dfrac{1\times1\times1\times4}{1\times1\times1}\)

\(=4\)

Ta có: \(1996\cdot1995-996-100-1996\cdot1994\)

\(=1996\left(1995-1994\right)-1996\)

\(=1996-1996=0\)

Ta có: −996−1000

=(1996⋅1995−1996⋅1994)−(996+1000)

=1996(1995−1994)−1996

=1996−1996

=0

=\(\frac{399x\left(45+55\right)}{1995x\left(1996-1991\right)}\)

=\(\frac{399x100}{1995x5}\)

=\(\frac{399x4x5x5}{399x5x5}\)

=\(\frac{4}{1}\)

=\(4\)

= \(\frac{17955+21945}{3982020-3972045}\)

= \(\frac{39900}{9975}\)

= \(\frac{7980}{1995}\)

= \(\frac{1596}{399}\)

= \(\frac{532}{133}\)

Aswer : \(\frac{532}{133}\)